1. Field of the Invention
The present invention relates to a high-flow concrete additive and a concrete material containing the additive. More specifically, it relates to a high-flow concrete additive which is added to concrete structures for civil engineering, architecture and concrete articles, in order to provide high flowability, high self-compactability and high segregation resistant properties to fresh concrete, reduce or render unnecessary compaction during placement, and minimize noise during construction for an improved working environment while also facilitating concrete placement, as well as to a polymer which may be used as such an additive.
2. Description of the Related Art
Recent years have seen an increase in the demand for high-flow concrete, due to the greater complexity and diversification of concrete structures for simplification of operations at construction sites, as measures against noise during shake compaction, as preventive measures against earthquakes and for beautification of the environment. Fresh concrete has traditionally been given higher flowability by addition of water or water reducing agents. However, this alone causes segregation of the concrete material, which allows intermixture with the coarse aggregates and thus reduces the self-compactability and makes it impossible to obtain uniform concrete, resulting in lower concrete quality. For this reason, addition of water-soluble polymers is being investigated for the purpose of controlling such material segregation.
Commonly used water-soluble polymers include cellulose derivatives such as methyl cellulose ether, hydroxypropylethyl cellulose ether, methylhydroxyethylmethyl cellulose ether, hydroxyethyl cellulose ether and hydroxypropyl cellulose ether, as well as polysaccharides, curdlan, dextran, starch, xanthan gum, polyacrylamide, and the like. However, when these water-soluble polymers are added in an amount sufficient to control material segregation, they increase the viscosity of the fresh concrete, causing the problem of lower flowability (Japanese Unexamined Patent Publication No. 5-139806).
When used together with water reducing agents which are used to increase the flowability of fresh concrete, they usually interact with the water reducing agents to obstruct the flowability. This obstruction makes it extremely difficult to ensure both the desired viscosity and flowability (Japanese Unexamined Patent Publication No. 6-293542, No.8-12397). In addition, cellulose derivatives and other saccharides cause a variety of problems including long-term storage difficulties due to decay while in aqueous solution.
Japanese Examined Patent Publication No. 2-23566 discloses a copolymer of an N-vinylacetamide compound and 2-acrylamido-2-methylpropanesulfonate as a water-soluble polymer for control of material separation, but since it is used as a water-soluble boring aid, the reduction in flowability over time has not been considered a problem.